Retention of urine, leading to complications such as urinary tract infection and urinary calculi, remains a major factor leading to morbidity in individuals with neurologic disorders or injury such as spinal cord injury. In high cord injury, with upper motor neuron damage, the lower nerve pathways to the bladder are intact. The aim of micturition control in these individuals is to enable them to contract the bladder musculature without direct or reflex activation of structures in the urethra that may impede urine flow. The procedure should leave an acceptable post-void residual volume within the bladder and should also be able to prevent overflow incontinence.
Previously, electrical stimulation has been applied to control the bladder and bowel. These previous attempts have predominantly focused on activation of the detrusor by sacral root or nerve stimulation, activating either motor or sensory nerves. The methods can suffer from the problem of contraction of the bladder to expel urine concurrently with contraction of the external urethral sphincter blocking urine flow. Extensive sacral dorsal rhizotomy is carried out to solve this problem in individuals with spinal cord injury. The rhizotomy technique also results in the loss of sensation and reflexes such as reflex erection in males. It would be advantageous if reflex contraction of the sphincter could be reduced or eliminated without the losses caused by the rhizotomy technique. Using continuous stimulation to activate sensory nerves to evoke reflex bladder contractions frequently results in smaller reflex bladder contractions and reduced efficiency of urine expulsion. It would be advantageous if reflex contractions of the bladder were more robust.